What's an IME?
- An "Input Method Extension" is the software that allows you to type Japanese (or other languages) on your computer.
See your distribution documentation for more details, there are several ways to input foreign characters under Linux. The most popular method is a combination of programs.
- Smart Common Input Method (SCIM) -- SCIM is a front-end to various back-end modules for different languages. There are back-end modules for Japanese, Chinese, Korean, Swahili, Arabic, you name it. SCIM provides a central place to select and configure these various back-end modules.
- Anthy -- Anthy is a Japanese input module that provides Hiragana, Katakana input and dictionary lookup for Kanji.
Most Linux distributions make this easy for you by providing packages that you can just install and be done with it. For instance, in my distribution (Gentoo) I just had to install the 'scim' and 'scim-anthy' packages.